The easiest way to explain it is to point out that in meditation your mind is focused on something.
On one thing.
A mantra, a guided meditation, your breathing, whatever it may be that you are holding your focus on.
And for beginners, your mind may not be used to such focus, even for short periods of time.
When we meditate and practice focus it is often very relaxing. Often people get actual “rest” while meditating, which they may not be getting if they suffer from restless sleep. (rest-less) (Yes you can sleep and not get any rest, and that is what is happening when you wake up in the morning as tired or more tired than when you went to bed.)
But even very experienced meditators can experience what I call “the slingshot effect,” or “mood swings,” from meditation.
Your mind is focused on one thing, you are very peaceful and relaxed, and then after meditation it is “back to the real world.”
Which can be very disturbing.
The mind is not used to so much peace and it may be trying to adjust to it. When suddenly you find yourself in a crowded grocery store, or several people will speak to you all at once.
And you are easily overwhelmed.
For quite some time I noticed that if I had a very focused meditation, the next day I would feel chaotic all day. And if I had a meditation that wasn’t so focused, the next day I would be like the Buddha himself.
People who meditate can also become very sensitive.
We are increasing awareness, awakening to a higher consciousness, and so we notice things around us much more than we used to.
I’ve been meditating regularly for a long time, so I am aware that I go through different phases with it.
It has gotten a lot easier for me to remain detached when things seem to overwhelm me or when I have a giant mood swing.
We can sometimes get mood swings and sometimes we get easily overwhelmed, but meditation is teaching us that we are not the mood swings. We are not all of the chaotic feelings either.
We are awareness. We are consciousness. We must continue to expand this a little at a time.
Find a meditation practice that works, and do that.